The objective of the study is the prospective assessment of possible correlations between body iron stores of two through six year old children and their performance in a battery of psychological tests including measures of physical activity, attention, motivation and IQ. Three groups of children represent the total sample: (1) 240 controls (C); (2) 120 sideropenic children without anemia (I); and (3) 60 sideropenic children with anemia (IA). The study design requires a first psychological evaluation (Time1) following the laboratory analysis and physical exam which should have identified the children for the (C), (I) and (IA) groups. Six months later (Time2), again following laboratory analysis and physical exams, the psychological evaluation will be repeated. From Time1 to Time2 children in Group (IA) and half of the (I) sample will be placed in iron repletion therapy. The other half of group (I) will receive no treatment, as is the case with the control children. Recognizing that possible associations between low body iron and low performance in the battery of psychological tests may be due to social-environmental factors or general nutritional status the research design includes partial control of these two sets of variables. Information on economic status and developmental history and organization of the children's families will be collected via interviews with the mothers. Height, weight and skinfold thickness measures will be obtained in all children. The study design yields a "group x variable x time" data frame. The basic concepts for data analysis are: interindividual differences, intraindividual changes, and intraindividual differences.